The present invention is directed to a drilling tool for drilling and/or chiseling devices, particularly for drilling in masonry, concrete, rock and similar hard materials. The drilling tool has a shank and a shaft containing two helical removal grooves with a drill head at one end of the shaft containing a cutting plate. The cutting plate is inserted into the drill head and projects in the axial direction of the shaft out of the drill head and has a dimension extending perpendicularly of the axial direction greater than the diameter of the drill head. In the region of the drill head, the removal grooves extend essentially parallel to the axis of the shaft.
It is well known for producing boreholes in a hard receiving material, such as concrete, rock, masonry and similar hard materials, to use a drilling tool as disclosed in the German Offenlegungsschrift 27 35 227 which has a cutting plate formed of a hard alloy inserted into a recess in the drill head. The cutting plate of this known drilling tool has a rectangular cross section extending essentially at right angles to the axial direction of the drilling tool. The dimension of the cutting plate extending at right angle projects radially outwardly from the drill head at two diametrically opposite sides. The cutting plate has a dimension extending parallel to the axis of the drilling tool. In the region of the cutting plate projecting outwardly from the drill head there is a cutting tip. On the opposite side the drill head from the cutting tip there is a shaft with a helical removal groove for carrying drillings out of the borehole.
In comparison to the diameter of the drilling tool, the thickness of the cutting plate perpendicular to the dimension extending across the drill head and perpendicular to the axis of the drilling tool is very small. During the drilling operation, very high stresses are developed in the opposite outer end regions of the cutting plate. On one hand, these very high stresses are caused by a high peripheral speed, and, on the other hand, by high forces acting on the cutting plate during the cutting operation. As a result, the radial end regions of the cutting plate are subject to greater wear than the central region of the cutting plate. Due to these high stresses, damage can occur to the cutting plate.